Vessel with machinery modules outside watertight hull

ABSTRACT

The invention is directed to an improved vessel configuration for high speed ships such as Naval Destroyers. The vessel has a long, slender tumble home (inward-sloped topsides) watertight hull and a deckhouse structurally integral with the watertight hull. All main machinery is modular and outside the watertight hull, freeing midship areas for personnel. Two removable, prealigned and pretested, steerable propulsor modules are attached to the stern after construction and are replaceable pierside. Each propulsor module includes a steerable pod aligned to the water inflow, a steering cylinder, and a streamlined strut connecting the pod to the steering cylinder. Two removable, power modules are mounted above the weather deck in a deckhouse. Each power module includes an intercooled, recuperated gas turbine, a ship-service alternator, and a propulsion alternator. The present vessel provides global range, reduced lightship displacement, reduced cost, superior seakeeping, no seawater ballast, sharper turns and stops, and greatly reduced installed power, fuel consumption, and pollution.

STATEMENT OF GOVERNMENT RIGHTS

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to an improved vesselconfiguration for high speed ships such as Naval Destroyers and, moreparticularly, to a vessel having a watertight hull with no penetrationstherein for propulsion machinery wherein all main machinery is modularand is located outside the watertight hull.

2. Brief Description of Related Art

Ever since steam powered propellers replaced wind powered sails as themain means of propelling ships, the powerplant has occupied the centerof the hull. The midship located powerplant has been connected by long,heavy shafts to aft mounted propellers. Steering has generally beenprovided by rudders aft of the propellers. From the middle of thenineteenth century to the present the overwhelming proportion of theworld's surface combatants and cargo ships have shared thisconfiguration.

The Great White Fleet of Teddy Roosevelt's era, the four stackeddestroyers of World War I, and the entire World War II fleet areexamples of such designs. Nuclear powerplants introduced into Navalcruisers and destroyers merely substituted for the boilers, fuel tanks,and turbines of their fossil-fueled predecessors.

When compact, aircraft-derivative gas turbines were introduced in theSpruance class destroyers in the seventies, the powerplant configurationwas little changed from those preceding it. The Ticonderoga classcruisers of the eighties and the Arleigh Burke class destroyers of thenineties retain this same powerplant configuration. For surfacecombatants with maximum Froude Numbers exceeding 0.4, this configurationcan cause the cost of the mechanical and electrical systems to exceedfour times the cost of the hull structure.

For high speed ships, wavemaking resistance increases dramatically withspeed. Resistance of a bare-hull can be divided into a viscous componentand a wavemaking component. For ships at low speeds, viscous resistancepredominates, whereas at sustained speed (speed at 80% of full power)and maximum speed (speed at full power), large wavemaking resistance isadded. Wavemaking resistance is somewhat dependent on hull shape,heavily dependent on "fatness," and varies sharply with thedimensionless Froude Number [Fr=V/(gL)⁰.5, where V is ship speed, g isthe gravitational constant, and L is length at the waterline].Wavemaking resistance is very small compared to viscous resistance atFroude numbers below about 0.34, but then it rises sharply so that at aFroude number of about 0.45, its value is several times that of viscousresistance. Furthermore, the open shafting of high speed Navalcombatants typically adds 45% to the viscous resistance of the barehull.

For displacement monohulls, to minimize the cost of the power systems,the hull should be long enough that the sustained speed is reachedwithout wavemaking resistance becoming predominant. Preferably, theFroude number should not exceed 0.38 at sustained speed. In the past,the Navy design philosophy was that propulsion systems were preordained,of fixed cost and size, and that ship cost was best reduced by makingthe ship as short as possible. The 466 foot length Arleigh Burke class"short" destroyer represents the philosophy of trying to save cost byshortening the hull. However, shortening the hull increases Froudenumber, and thus wavemaking resistance, at a given speed. Increasedresistance translates to increased power required for a given speedwhich, in turn, increases the fuel consumption over time. In addition,at a constant fuel capacity, ship resistance is approximately inverselyproportional to ship range.

A conventional, prior art ship design having vertical topsides 10 isdepicted in FIGS. 1-4. Centrally located powerplants 12 and propulsionshafting 14 are installed in the hull early in the overall shipconstruction process. As shown in FIGS. 3 and 4, powerplants 12 aregenerally located in one or more large main machinery rooms 16 that,along with required air intake ducting 18 and exhaust ducting 20, occupya large volume near midships. It is prohibitively costly to remove andreplace much of the main machinery systems once installed. Removingpropulsion power generation machinery 22, propulsion transmissionmachinery (shafting 14 and gears 24), or ship-service electricalgeneration machinery 26 and 28 would require cutting large holes in theside of the hull. Consequently, these machinery systems are designed tohave very low stresses and are thus exceedingly heavy and costly.Lightly loaded "safe" gears are a high weight legacy of thisconfiguration. A second legacy is long, heavy shafting, which is costlyto align. A third legacy is large air intake and exhaust ducting (in gasturbine powered ships, the air intake and exhaust uptake ducting aretypically very large), which occupy much of the upper decks andsuperstructure. The weight and required space for shafting and ductingmay add 50% to the weight and space requirements of the main electricand power producing machinery. Moreover, highly desirable spaces nearthe center of gravity of the ship, where ride motion is minimal, arededicated to machinery and ducting, not to personnel living and workingquarters. Furthermore, repairs are generally conducted in situ, often ininconveniently cramped quarters.

Further inefficiencies are introduced by the ship-service powergeneration machinery 26 and 28. Ship-service power (power other thanpropulsion power) has typically been produced by small turbines thatoperate at a low fraction of their design power and thus have netefficiencies near 15%. As a result, as much as one quarter of the fuelconsumed at cruise speeds is used for "hotel loads" such as heating,ventilation, air conditioning, lighting, food and fresh waterproduction, fire protection, i.e., non-propulsion related, ship-servicepower.

Moreover, hulls have customarily been designed for transverse stabilityand roll frequency at full-load displacement (full payload includingfull-fuel-load) with the required beam for stability being constantabove the design waterline, i.e., vertical topsides 10 as shown inFIG. 1. To maintain transverse stability throughout the mission, shiphulls designed for stability at full-load require sea water ballast tocompensate for expended fuel. In the past, as fuel was burned, sea waterwas pumped into the fuel tanks, and was then pumped out upon refueling.However, using emptied fuel tanks for ballast water increases pollutantsdischarged from the ship as "dirty" ballast is pumped into surroundingwater. In accordance with international pollution control limits, futurefuel tanks may not be ballasted by dischargeable water. The current Navyprocedure is to build excess clean water ballast tanks. Excess ballasttanks, however, are wasteful of ship space, and carrying seawaterincreases fuel consumption late in the mission.

The price of the conventional prior art ship configuration is increasedinitial cost, increased fuel cost, and decreased capability.Consequently, there is a need to provide a more affordable, morecapable, less polluting vessel. Such a vessel should use internal spacemore effectively than conventional vessels and should have adequatetransverse stability without adding ballast as fuel is burned. Thepresent invention is intended to overcome problems associated with priorart ship designs.

OBJECTS OF THE INVENTION

Accordingly, it is an object of the present invention to provide anaffordable, capable ship having lower resistance, reduced powerrequirements, reduced fuel consumption, and reduced environmental impactwhen compared to conventional monohulls (as described above) withsimilar missions.

It is a further object of the present invention to provide a ship havingsimplified fabrication and reduced initial costs, as well as simplifiedmaintenance and reduced operating and maintenance costs.

It is a yet a further object of the present invention to free midshipspaces for more effective use as personnel living and working areas.

It is still a further object of the present invention to provide a shiphaving reduced wake, acoustic, infrared and radar detectability.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art upon a reading of the followingdetailed description taken in conjunction with the drawings and theclaims supported thereby.

SUMMARY OF THE INVENTION

The foregoing objects and advantages result from an innovativemachinery-driven ship design centered on simplicity and efficiency. Inaccordance with the present invention, an improved vessel having mainmachinery modules located outside a watertight tumble home hull isprovided.

The vessel includes a watertight hull having a stem bow and a tumblehome hull configuration comprising a longitudinally extending hullbottom having a maximum beam corresponding to the uppermost port andstarboard extensions of the hull bottom, port and starboardinward-sloped topsides extending upward from the uppermost port andstarboard extensions of the hull bottom, a longitudinally extendingweather deck disposed between the uppermost longitudinally extending endof each port and starboard topside, and a substantially vertical aft enddisposed between the aft ends of the port and starboard topside, thehull bottom, and the weather deck. The maximum beam corresponds to thezero-fuel-load design waterline of the vessel. All propulsion shaftingis located outside the watertight hull in aft mounted propulsor modules,consequently, no penetrations of the watertight hull for accommodatingpropulsion shafting are necessary. The vessel further includes adeckhouse structurally integral with the primary structural girders ofthe vessel. The deckhouse is located above the weather deck at asubstantially centrally located portion of the vessel. A compositematerial steeple is attached to the deckhouse and contains rotating andstationary antenna in coaxial alignment therein.

A plurality of pretested, prealigned, removable propulsion modules aremounted outside of the watertight hull. The propulsion modules areinstalled after construction of the watertight hull and further areremovable and replaceable without drydocking, thereby loweringmaintenance costs. The propulsion modules comprise at least onesteerable propulsor module and at least one power module. The steerablepropulsor modules are attached to the stern of the watertight hull andprovide means for both propelling and steering the vessel. The powermodules may be mounted above the weather deck, preferably in thedeckhouse, or directly above the propulsor module, or a combination ofthe two locations. Each power module includes therein power producingmeans capable of providing both ship-service power and propulsion power.Each power module is in electrical communication with one of thesteerable propulsor modules for providing propulsion and steering powerto the steerable propulsor module.

Each propulsor module includes a steerable pod aligned to the waterinflow. An integrated machinery capsule, inserted into the front end ofthe pod, drives contrarotating tractor propellers that reduce powerrequirements, wake detectability, and sonar detectability. Theintegrated machinery capsule contains seals, thrust bearings,contrarotating reduction gears, and an alternating-current electricmotor. A streamlined strut connects each pod rigidly to a rotatablebarrel shaped machinery room containing steering machinery andindividually replaceable propulsion auxiliaries. The rotatable barrel ismounted in a large diameter roller bearing fixed to the bottom of thepropulsor module housing and is rotated by a two-stage orbital gear andelectric drive that are attached to the roller bearing. By rotating thebarrel, the attached strut and steerable pod are rotated, thus,providing the variable thrust vector to steer the vessel.

Each power module includes a gas turbine, a ship-service alternator, anda propulsion alternator. Since each power module is located outside thewatertight hull, rather than deep in the midships section, inlet andexhaust ducts are short and light with low pressure drop to enhanceturbine efficiency.

The present invention results in a vessel wherein all main machinery ismodular, is located outside the watertight portion of the hull, isinstallable after hull construction has been completed, and is piersidereplaceable. The vessel has a tumble home hull, i.e., a hull havinginward-sloped topsides. The vessel is long and slender, having a Froudenumber at sustained speed <0.38, thus requiring reduced power atsustained and maximum speeds when compared to conventional high speeddisplacement hulls. The deckhouse, which may include a helicopterhanger, is a structurally integral part of the hull girders, thusreducing structural weight and reducing vulnerability to structuraldamage. A composite material steeple containing fixed and rotatingcommunication and radar antennas is attached to the top of thedeckhouse.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects and other advantages of the present invention willbe more fully understood by reference to the following description takenin conjunction with the accompanying drawings wherein like referencenumerals refer to like or corresponding element throughout and wherein:

FIG. 1. is a body plan of a prior art monohull having vertical topsides.

FIG. 2. is an isometric view of a prior art monohull.

FIGS. 3a. and 3b. are top and side views, respectively, of a prior artmonohull showing conventional arrangement of main machinery.

FIGS. 4a. and 4b. are top and side views, respectively, of centrallylocated main machinery rooms on a conventional prior art monohull.

FIG. 5. is a body plan of a tumble home hull configuration in accordancewith the present invention.

FIG. 6. is an isometric view of a tumble home hull configuration inaccordance with the present invention.

FIG. 7. is an isometric view of a preferred embodiment of the presentinvention.

FIG. 8. is a cutaway side view of a preferred embodiment of the presentinvention.

FIG. 9. is a top view of a deckhouse showing deckhouse mounted powermodules.

FIG. 10. is a side view of the stern section of the present inventionshowing stern mounted propulsor and power modules.

FIGS. 11a. and 11b. are top and side views, respectively, of the mainstructural members of the present invention.

FIG. 12a., 12b., and 12c. are cross-sectional views taken along lines12a, 12b, and 12c, respectively.

FIG. 13. is an exploded view showing the decks of FIG. 14.

FIG. 14. is a side view of the present invention showing machinerymodules mounted outside the watertight hull.

FIG. 15. is an isometric view of the power modules of the presentinvention.

FIG. 16. is an isometric view of the propulsor modules of the presentinvention.

FIG. 17. is an exploded view of the propulsor modules of the presentinvention.

FIG. 18. is a stern view of the present invention.

FIG. 19. is an isometric view of the stern of the present inventionshowing the retractable stern flap.

FIG. 20. is a cross-sectional view of the rotatable barrel of thepresent invention.

FIG. 21. is a top view of the steering means of the present invention.

FIG. 22. is a cross-sectional view of the streamlined strut of thepresent invention showing the circulation control valve.

FIG. 23. is a cross-sectional end view of a ring-ring bicoupledcontrarotating epicyclic reduction gear of the present invention takenalong line 23 of FIG. 24.

FIG. 24. is a cross-sectional side view of a ring-ring bicoupledcontrarotating epicyclic reduction gear of the present invention takenalong line 24 of FIG. 23.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A systematic description of the design considerations that resulted inthe present invention are presented in two published reports: [1]Levedahl, William J., Samuel R. Shank, and William P. O'Reagan,"DD21A--A Capable, Affordable, Modular 21st Century Destroyer,"Carderock Division Naval Surface Warfare Center reportCARDIVNSWC-TR-93/013, December 1993, pp. 1-266; and [2] Levedahl,William J., "A Capable, Affordable, 21st Century Destroyer," NavalEngineers Journal, Vol. 103, No. 3, May 1993, pp. 213-223. These tworeports, authored by the inventor and describing the present invention,are incorporated herein by reference.

Referring now to the drawings, and particularly to FIGS. 5-8, thepresent invention comprises watertight hull 40 having stem bow 42 and atumble home configuration. Herein, "tumble home" refers to a hull havingtopsides 44 (generally the hull sides above the waterline) having aninward-sloped angle relative to vertical. Although in the preferredembodiment, the tumble home angle is constant, more than one angle tothe vertical is within the scope of the present invention.

Watertight hull 40 comprises longitudinally extending hull bottom 46,port and starboard tumble home topsides 44 extending upward from portand starboard uppermost extensions 54 of hull bottom 46, longitudinallyextending weather deck 48 disposed between uppermost ends 50 of port andstarboard topsides 44, and a substantially vertical aft end 52 disposedbetween aft ends of port and starboard topsides 44, hull bottom 46, andweather deck 48. The maximum beam is defined by port and starboarduppermost extensions 54 of hull bottom 46 and corresponds to thezero-fuel-load design waterline (DWL) of the vessel.

Watertight hull 40 is separated longitudinally into a plurality ofsurvivable watertight compartments 56 each of the compartments having atleast one auxiliary machinery module 58 mounted therein. There are nopenetrations of bulkheads 57 of compartments 56 for accommodatingpropulsion power generation or transmission machinery. Each auxiliarymachinery module 58 includes heating means (e.g., electric heater, heatpump), air conditioning means (e.g., air conditioner, heat pump),ventilation means (e.g., fans), fire suppression means (e.g., watersupply and pump connected to separate self contained fire extinguishmentsystem located in each compartment), and backup electric power means(e.g., batteries, generator). Heating, air conditioning, ventilation,fire suppression, and backup electric power means all compriseconventional hardware and are, therefore, shown only schematically inFIGS. 8 and 13 as auxiliary machinery modules 58. A heat pump, usingseawater as a source or sink, is a preferred means of heating and airconditioning.

Deckhouse 60 is structurally integral with watertight hull 40. Deckhouse60 is located above weather deck 48 at a substantially centrally locatedportion of the vessel and, in combatants, preferably includes helicopterhanger 62, which houses, among other things, helicopters 64 andauxiliary boats 66. Deckhouse 60 is preferably made of structural steelto provide protection from explosions to deckhouse mounted machineryequal to protection provided to conventional hull mounted machinery.Composite material steeple 68 is attached to deckhouse 60. A constanttumble home angle throughout the hull topsides, continues uninterruptedinto deckhouse 60 and steeple 68. Composite materials for steeple 68include fiber reinforced matrix materials such as fiberglass and carbonreinforced organic resin matrix materials. Composite material steeple 68contains rotating and stationary communication and radar antennas 70 incoaxial alignment therein, each of antennas 70 transmitting within anarrow frequency range. The inside walls of composite material steeple68 may have radar-reflective coatings or shielding (not shown) thereon.The coatings or shielding are operative to reflect radar originatingfrom without the vessel but allow a narrow-band transmission from theantennas. For example, selective shielding may be provided by analuminized mylar shield having the aluminum coating etched off to fromslots that allow specific wavelengths to pass through. Longerwavelengths require larger slots. Combatants may include armaments suchas main 5"/54 calibre guns 72, close in weapons system 74, VerticalLaunch System 76, and other high energy weapon systems.

The tumble home topsides 44 of watertight hull 40 preferably have aconstant inward slope angle of between about 10° and about 12° tovertical. However, multiple angles to the vertical are an alternative.If more than one angle is employed, to reduce radar reflection theangles shall not intersect at a 90° angle. Watertight hull 40 mayfurther include flared topsides 78 below the weather deck and flaredbulwarks 80 above the weather deck. Flared topsides 78 and bulwarks 80extend aft from stem bow 42.

A constant tumble home angle throughout the hull topsides, continueduninterrupted into the deckhouse and steeple, minimizes the number ofangles from which radar return is received. This hull characteristic,combined with the elimination of right-angles at any intersection,decreases detectability from ships, surface-skimming missiles, andsatellites. A clean outer surface enhances the low radar cross-section;most deck machinery, bitts, bollards, cleats, stanchions, lifelines,etc., should be hidden from view, designed for low radar reflection(e.g. conformal), be non-metallic where possible, and preferably beretractable. Rotating antennas 70 are coaxially mounted in steeple 68,thus reducing radar reflection and maintenance. A constant tumble homeangle of between 10° and 12°, reduces radar cross-section by over 40 dB(a factor of more than 10,000) compared to conventional vertically sidedships (as shown in FIGS. 1-4).

Referring to FIGS. 11-13, primary structural members of watertight hull40 include two longitudinally continuous box girders 82 andlongitudinally continuous keel 84. Additional primary strength membersinclude outer shell plating 86, inner hull sides 88 and bottom 90, topsurface 92 of deckhouse 60, and forward transverse side 94 of deckhouse60. The box girder configuration of the present invention increases theprobability of survival after shallow-water mine explosions because itresists whipping deformations of the hull. The box girders 82 also serveas continuous ducts along each side of the hull just below weather deck48 and, thus, may carry all longitudinal piping and electricalcommunication and transmission means. Thus, watertight hull 40 requiresno penetrations to accommodate propulsion machinery except for one ormore apertures in at least one box girder 82 for accommodatingtransmission of electric power from at least one power module 100 to atleast one steerable propulsor module 98. Additionally, by placing alllongitudinally running ducts, cables, lines, pipes, and conduits withinbox girders 82, no penetrations of bulkheads 57 are required.

Box girders 82 and keel 84 extend substantially from stem bow 42 to aftend 52 of watertight hull 40. Box girders 82 define an intersection ofinward-sloped topsides 44 and weather deck 48 and extend from weatherdeck 48 downward one deck (nominally 9 ft). The portion of box girders82 adjacent deckhouse 60 extend upward from weather deck 48substantially to deckhouse top surface 92 and define longitudinallyextending inward-sloped sides of deckhouse 60. Structurally integraldeckhouse 60 increases the hull-girder section modulus over thelongitudinally central part of the ship which incurs the maximum hoggingor sagging moments, thereby permitting reduced thickness and weight ofthe girder members. Box girders 82 preferably contain a plurality oflongitudinally extending electric cables 83 and fluid carrying pipes 85therein. Additionally, at least one of box girders 82 preferablycontains longitudinal walkways (not shown) functioning to providepersonnel access, through watertight doors in the girders, among theplurality of survivable compartments 56.

A basic damage stability requirement exists. The ship must be stablewith any two adjacent compartments 56 flooded. Since there are no mainmachinery systems (i.e., main propulsion and ship-service powergeneration machinery) inside watertight hull 40, the long machinerycompartments 16 and large vertical trunks that contain air duct 18 and20, which are present in conventionally configured hulls (see FIG. 3-4),do not exist in the present invention. Consequently, watertight hull 40can be compartmented freely to meet the damage stability requirements.Furthermore, as shown in FIG. 14, the deck heights can be uniform and ofconstant height, which is not possible in conventional ships havinglarge machinery compartments amidships. Consequently, ship volume may bereduced. Watertight hull 40 is separated longitudinally into a pluralityof survivable compartments 56, each containing its own auxiliarymachinery module 58. Each survivable compartment 56 is self-sufficientexcept for long-term electric power. No air, gas, or liquid linespenetrate compartments 56, except those from box girders 82 (i.e., nocompartment bulkheads 57 are penetrated). Girder mounted and compartmentmounted electric lines or cables communicate electrically throughconventional watertight electric connector plugs mounted in the girderwall adjacent each compartment. All liquid or gas pipes that penetrategirders 82 into compartments 56 are sealed at the penetration and haveconventional shutoff valves on each side of the girder wall.

A plurality of watertight, insulated electrical connector plugs 87penetrate the wall of at least one box girder 82. At least one of plugs87 is located adjacent each of compartments 56. Each plug 87 is inelectrical communication, by way of transverse branch cable 89, with atleast one of longitudinally extending cables 83 in box girders 82 and isfurther in electrical communication with at least one cable 91 incompartment 56. In addition, a plurality of transverse fluid carryingbranch pipes 93 penetrate the wall of at least one box girder 82adjacent compartments 56. At least one of pipes 93 is located adjacenteach of compartments 56. Each transverse pipe 93 is in flowcommunication with at least one longitudinal pipe 85 in girder 82 and isfurther in flow communication with at least one pipe 95 in compartment56. [Herein, when two elements are said to be in "flow communication"they are interconnected so as to be in flow communication by, forexample, such well known interconnecting means as ducts, conduits,pipes, tubes, hoses, or any other suitable means for transporting afluid.] Each transverse pipe includes a sealing means thereon, such asan O-ring, gasket, or other suitable well known sealing means (notshown), operative to create a watertight seal between the pipe and thebox girder. Further, each transverse pipe includes a shut-off valve 97on each side of the box girder wall.

Referring to FIGS. 7-10 and 15-17, a plurality of pretested, prealigned,removable propulsion modules 96 are mounted outside of watertight hull40. Propulsion modules 96 are installable after construction ofwatertight hull 40 and are removable and replaceable pierside withoutdrydocking. Propulsion modules 96 comprise at least one steerablepropulsor module 98 and at least one power module 100. Steerablepropulsor modules 98 are attached to aft end 52 of watertight hull 40and function to both propel and steer the vessel. Power modules 100 maybe mounted above weather deck 48, preferably in deckhouse 60 (see FIGS.7-9), or directly above propulsor modules 98 (see FIG. 10), or acombination of the two locations. When mounted above propulsor modules98, power modules 100 will include outer housing 101 forming a naturalextension to watertight hull 40.

Each power module 100 preferably includes therein an intercooled,recuperative (ICR) engine 102, a ship-service generator 104 powered byICR engine 102 and functioning to provide non-propulsion related powerto the vessel, and a propulsion generator 106 operatively connected witha propulsor module 98 to provide electric propulsion and steering powerto propulsor module 98. Herein, "non-propulsion related power" refers tothe maximum daily ship-service load experienced by the ship, i.e., allelectrical power needed for routine, emergency, and combat operationsthat is not used by propulsor modules 98 to propel or steer the ship.Each intercooled, recuperative engine 102 includes a gas turbine 108, anintercooler 110 integral with the gas turbine, and a recuperator 112integral with the gas turbine. Intercooler 110 and recuperator 112 areattached to gas turbine 108 and are incorporated into the normal enginecycle. Intercooler 110 cools air entering the high pressure compressorwhile recuperator 112 uses gas turbine exhaust air to pre-heat thecombustion air and, thus, reduce fuel consumption over the full powerrange. Although an ICR gas turbine is preferred, any appropriately sizedsimple cycle gas turbine, such as for example General Electric LM2500gas turbines used in present Naval destroyers or Rolls-Royce RB-211 aeroengine family gas turbines, are within the scope of the presentinvention. Propulsion generator 106 includes a winding to provideelectric propulsion power to a propulsor module 98 and may furtherinclude a coaxial high voltage winding capable of powering high energyweapon systems.

Additionally, the vessel may include a conventional battery energystorage system (shown schematically as 114) for providing ship-servicepower in the event the ship-service generator 104 fails or is taken offline. Battery energy storage system 114 employs ordinary lead acidbatteries and large inverters that are distributed appropriatelythroughout the vessel, preferably in auxiliary machinery rooms,auxiliary machinery modules 58 within each compartment 56, rotatablebarrel 134, and other appropriate locations.

In the present invention, the main propulsion turbines are no longerwithin the confines of the watertight hull, thus air ducts are removedfrom the watertight hull freeing midships space for personnel use. Asmore fully described below, short, light, turbine air inlet 116 withside or aft facing inlet louvers 117 and inlet ducts 118 are mountedabove and in flow communication with air intakes of deckhouse mountedpower modules. If one of power modules 100 is mounted atop one ofpropulsor modules 98, as shown in FIG. 10, air inlet 116 will remainlocated atop deckhouse 60. However, inlet ducts 118 will run from powermodule 100, along the interior of continuous box girder 82, to air inlet116.

The tumble home configuration of the present invention allows theengines to exhaust over-the-side (abeam) and downward without theexhaust ducts extending beyond the waterline beam of the ship andwithout occupying internal ship volume. As shown in FIG. 18,short-ducted, downward facing, infrared shielded, boundary layer airinduction-cooled exhaust system 120 minimizes infrared detectabilityfrom any point above the horizon. Exhaust system 120 includes shortover-the-side exhaust duct 122, mounted abeam and in flow communicationwith the exhaust of each power module 100, boundary-layer-inductionsignature suppressors (BLISS) 124, and radar reflecting exhaust caps126. Radar reflecting exhaust caps 126 preferably have tumble homeangles equal to those of watertight hull 40. Exhaust system 120 will belocated adjacent power module 100 whether power module 100 is mounted indeckhouse 60 or atop propulsor module 98. If power module 100 is mountedin deckhouse 60, exhaust duct 122 will exhaust through a sidewall ofdeckhouse 60. Boundary-layer-induction signature suppressors (BLISS)systems exhausting upward are presently used with conventional shipboardgas turbines. When employed with the present invention, BLISS 124exhausts downward. BLISS 124 is in flow communication with inlet ducts118 and creates an unobstructed flow passage from inlet ducts 118 to theoutlet of exhaust ducts 122. The exhaust gases exiting exhaust ducts 122are at a lower pressure than the intake air and, thus, they draw coolair from inlet ducts 118 into the exhaust stream. Exhaust gasses fromICR engines are at lower temperatures than from conventional gas turbinepropulsion engines (e.g., General Electric LM2500 gas turbines), BLISS124 further dilutes exhaust gasses with cool air, and the exhaust isprojected downward and outward toward the water surface so that exhaustplumes 128 have low visibility from other ships or low flying missiles.Alternatively, a short vertical uptake exhaust system having exhaustducts mounted above the engines may be employed.

Steerable propulsor modules 98 form naturally shaped extensions towatertight hull 40 and will preferably define a transom stern 130 (seeFIG. 19), although a cruiser stern variant is an alternative. Eachsteerable propulsor module 98 comprises outer housing 132, substantiallyvertical rotatable barrel-shaped auxiliary machinery room 134 rotatablymounted within outer housing 132, axisymmetric steerable pod 136containing integrated machinery capsule 138 therein, and streamlinedstrut 140 rigidly connected at top end 142 to rotatable barrel 134 andrigidly connected at bottom end 144 to steerable pod 136. The number ofpropulsor modules varies according to the propulsion requirements of theship, however, all propulsor modules are attached to the stern of thewatertight hull. For example, a frigate may have one propulsor module,while a destroyer may require two, and larger hulls may be designed withthree or more propulsor modules.

Outer housing 132 is secured to aft end 52 of watertight hull 40 anddefines the vessel stern. Outer housing 132 forms the naturally shapedstern extension to watertight hull 40. Thus, outer housing 132 hastumble home topsides 145 extending aft from tumble home topsides 44.Transom stern 130 may have either a tumble home (inward-sloped) angle ora flare (outward-sloped) angle, the angle to vertical being equal to thetumble home angle of watertight hull 40. Streamlined strut 140 connectseach pod 136 rigidly to a substantially vertically aligned rotatablebarrel-shaped auxiliary machinery room 134. Each streamlined strut 140has the maximum possible longitudinal length to minimize interferencedrag. Each strut 140 may include port and starboard ejection ports 146for preferentially ejecting water to provide additional steeringcontrol. Manned entry into the rear of each pod from the machinery roomis through the after part of the strut. Access forward is via theforward extension of the strut. The rotatable barrel contains steeringmeans 148 and individually replaceable auxiliary propulsion machinerycomponents (not shown) that support the propulsor system. Auxiliarypropulsion machinery components may include oil pumps for thelubrication oil, heat exchangers (using seawater as the cooling medium)and water pumps for the coolant system, seals, and batteries forproviding emergency power. Steering means 148 includes geared electricmotor 150 and high-reduction-ratio gear system 151.

Referring to FIGS. 20 and 21, steering during major maneuvers isaccomplished by rotating pods 136 using rotatable barrel mountedelectric motor 150 and high-reduction-ratio gear system 151.High-reduction-ratio gear system 151 includes dynamically balanced,high-reduction-ratio, dual orbital gears 152 and 154 orbited by cammedrotor 155, three planet planetary gear set 156 with associated planetcarrier 157, sun gear 158 and ring gear 159, and gear system fixed ringgear 160. Lower orbital gear 152 and upper orbital gear 154 are 180° outof phase. Fixed ring gear 160 is rigidly mounted atop stationary member164 of moderately loaded, large diameter roller bearing 162. Fixed ringgear 160 and roller bearing 162 are rigidly attached to base 163 ofouter housing 132. Roller bearing 162 supports the entire steerable podand rotatable barrel system and transmits thrust to propulsor module 98and watertight hull 40. A plurality of vertical pins 168 pass throughholes in lower orbital gear 152 and upper orbital gear 154, and areimplanted in rotating base 166 at their bottom end and upper plate 170at their top end. Strut 140 is rigidly attached to rotating base 166which is attached to and rotates with gear system 151. Upper plate 170rotates with pins 168 and rotating base 166, and is connected to ringgear 159 of planetary gear set 156. Orbital gears 152 and 154 areorbited by cammed rotor 155 which is driven by electric motor 150through planet carrier 157 of planetary gear set 156. The holes inorbital gears 152 and 154 are larger than pins 168 by twice the cameccentricity. Thus, pins 168 prevent orbital gears 152 and 154 fromrotating relative to rotating barrel 134 but allows them to orbit.Orbital gears 152 and 154 each have one tooth less than does fixed ringgear 160. Consequently, rotating base 166 rotates through an anglecorresponding to one gear tooth for each revolution of cam rotor 155.Three plant planetary gear set 156 combined with a 90 tooth fixed ringgear 160 provide a reduction ration of over 1,000:1. Steering means 148is operative to rotate pods 136 rapidly through a 270° arc. Thus, fastturning or crashback is provided by rotating pods 136 through anappropriate angle. If two or more propulsor modules are employed, thepods are mounted such that the end of the pod aft of the axis ofrotation is short enough not to interfere with adjacent pods duringrotation.

Small steering correction are quietly made by preferential ejection ofcoolant system seawater through ejection ports 146 in the port andstarboard after-sides of struts 140, providing circulation controlthrough the Coanda effect. The coolant system water pumps, located inauxiliary machinery spaces of rotatable barrel 134, are in flowcommunication with circulation control valve 172 and ejection ports 146.Coolant system seawater is pumped from rotatable barrel 134 throughcirculation control valve 172 to either or both of ejection ports 146.Circulation control valve 172 may include any well known control valvefor providing preferential circulation to more than one outlet. As shownin FIG. 22, circulation control valve 172 may comprise a rotatable,cylindrical valve having slots 173 which align with ejection ports 146.By rotating valve 172, using for example an electric motor, flow may beclosed off from both of ports 146 or may be provided to one or both ofports 146.

Referring to FIGS. 16 and 17, each pod 136 has an open forward end 180and a pointed aft end 180. Pods 136 are aligned with the water flowaround the after-end of the vessel to provide axial flow into propellers184 during straight-ahead operation. Steerable pods 136 are preferablycylindrical and of the minimum diameter and length consistent with motordiameter and acoustic requirements (to accommodate acoustic mounts andacoustic insulation). Such pods produce less than half the resistance ofprior art open shafts and struts.

Each pod 136 has mounted therein a prealigned, pretested integratedmachinery capsule 138. Each integrated machinery capsule 138 containscontrarotating (CR) propeller shafts that extend forward of the pod openforward end and associated shaft seals and thrust bearings (representedschematically as 186), CR propellers 184 mounted on the forward end ofthe CR propeller shafts, and power means 188 functioning to rotate CRpropellers 184. Power means 188 preferably comprises a liquid cooledalternating-current electric motor 190 and contrarotating reduction gear192. Although CR propellers are preferred, conventional fixed pitch orcontrollable, reversible pitch propellers and their associated shafts,shaft seals, bearings and power means are also within the scope of thepresent invention.

Lightly loaded, CR tractor propellers, facing directly into theundisturbed flow stream outside the hull boundary layer, provide highefficiency and no cavitation up to 25 knots, except during sharp turnsand rapid accelerations. Contrarotating propellers 184 are preferablyhighly skewed propellers. Contrarotating propellers with seven bladesforward and five blades aft minimize both tip cavitation and acousticsignature. In addition, CR propellers sharply decrease the wakesignature by avoiding major wake vortex that brings cooler subsurfacewater to the surface.

A CR reduction gear system suitable for the present invention willreduce output rotational speed and increases total output torque ascompared to input rotational speed and torque. Any suitably sized priorart CR reduction gear system is compatible with the present invention.However, a ring-ring bicoupled contrarotating epicyclic reduction gearis preferred. Alternatively, the integrated machinery capsule maycontain CR propellers and shafts, seals, a thrust bearing, and acontrarotating DC acyclic superconductive hexapolar motor.

Referring to FIGS. 23 and 24, a simple epicyclic reduction gear (e.g.,first-stage epicyclic reduction gear 216 of FIG. 24) consistsessentially of: (1) a central, externally toothed sun gear 200 connectedto a rotating input shaft 202; (2) an internally toothed ring gear 204connected to an outer output-torque carrier and concentric with sun gear200; (3) one or more externally toothed planet gears 206, each of whichmeshes with both sun gear 200 and ring gear 204; (4) a planet carrier208 having spindles 210, one spindle central to each planet gear carriesthe net load on that planet gear; and (5) an inner output-torque carrier212 connected to planet carrier 208 and coaxial with sun gear 200 andring gear 204. The above described simple epicyclic reduction gearbecomes a contrarotating (CR) reduction gear when ring gear 204 isconnected to a rotating outer output shaft and inner output-torquecarrier 212 is connected to a rotating inner output shaft that rotatesin the opposite direction of the outer output shaft, as would be thecase when the CR gear is connected to CR propellers 184. The torque onplanet carrier 208, and thus the inner output shaft, is equal andopposite to the sum of the torques on input shaft 202 and the outeroutput shaft.

When the ratio between output and input torques needs to be larger thanthat achievable by a small diameter simple epicyclic gear, a "two-stage"epicyclic reduction gear may be used. In conventional two-stage "singlycoupled" CR reduction gear, the high-torque output of the first-stageepicyclic gear (a star gear if the planet carrier is non-rotating or aplanetary gear if the ring gear is non-rotating) is coupled to the sungear of the second-stage, CR, epicyclic gear.

A preferred CR reduction gear for use with the present invention is"ring-ring bicoupled contrarotating epicyclic reduction gear" 214 havinga two-stage epicyclic configuration with first-stage epicyclic gear 216and second-stage epicyclic gear 218 rotatably mounted in outer casing220, as shown in FIG. 24. Ring-ring bicoupled CR epicyclic reductiongear 214 is characterized by: first-stage planet carrier 208 beingconnected to second-stage sun gear 201 using interstage quill shaft 212;first-stage ring gear 204 and second-stage ring gear 205 being connectedto outer output shaft 222; and second-stage planet carrier 209 beingconnected to inner output shaft 224. All members of both stages rotateand carry useful torque. Ring-ring bicoupled epicyclic CR reduction gear214 provides the maximum reduction-ratio (maximum output torque) fortwo-stage reduction gears. Furthermore, the absolute ratio of inner toouter output torques is the minimum possible. Ring-ring bicoupled CRepicyclic reduction gear 214 also has lower centrifugal stress on thefirst-stage planet bearings than is the case with conventional CR gearshaving fixed ring gear first-stages and CR second-stages. Moreover,ring-ring bicoupled CR epicyclic reduction gear 214 includes vibrationsuppressing springs between all output gears and outer and inner outputshafts 222 and 224. Planet spindle springs 226 built into the shafts ofplanet carrier spindles 210, and ring gear radial springs 228 built intospacers between, and rotatably connecting, ring gears 204 and 205 andthe outer output shaft 222 provide means of reducing transmission ofvibration.

An exemplary ring-ring bicoupled CR epicyclic reduction gear with fourplanet gears in the first-stage and seven in the second-stage will powerCR propellers at a reduction ratio of approximately 30 to 1. In theseven-planet second-stage, each of the double-helical planet gearsmeshes with both sun and ring gears. The 28 meshes are out of phase, andeach planet gear has about 100 teeth so that individual toothengagements produce very small torsional accelerations. Flexiblespindles and flexible-tooth ring-gear holders greatly attenuatevibrations before they reach the shafts and propellers.

The present invention may further include stern flap 194 attached to atransom stern variant of propulsor module 98 (see FIG. 19). Stern flapsincrease the effective ship length and decrease Froude number and, thus,resistance at high speeds. Stern flap 194 may be fixed or retractable,and in either case will provide a natural extension to the hull bottomwhen deployed. If retractable, flap 194 is rotatably or pivotallymounted to the bottom of the transom stern to form a natural extensionto the hull bottom when extended. Retractable stern flap 194 is stowedsubstantially vertically against the stern of propulsor module 98. Sternflap 194 may be rotatably mounted in any conventional manner, such ashinge mounted on hinges 196. A retractable, variable angle stern flap194 may be extended and retracted using any well known, suitablereciprocating means 198 for biasing stern flap 194 to variablepositions, such as electric, pneumatic, or hydraulic powered ram, orelectric motor/worm gear driven retractable pivot arm. A retractable,variable angle stern flap is advantageous when fuel is burned withoutthe addition of seawater ballast. Under these conditions, displacementmay decrease 20-45% from full-load values, and transom submergence mayvary greatly. The flap can compensate advantageously for these changesin displacement as well as for changes in speed by producing trim andtransom submergence which maximize performance at all loadings.

Crew comfort is ensured by adequate transverse stability, tolerably lowroll frequency, good seakeeping in heavy seas, and crew working andliving quarters as near as possible to the ship's center of gravitywhere motions are at a minimum. The preferred embodiment of the presentinvention is designed for adequate transverse stability withzero-fuel-load (as opposed to present practice of designing forstability at full-fuel-load and adding sea water ballast as fuel isburned to retain stability). The maximum beam is located at thezero-fuel design waterline. Tumble home above the design waterlineprevents a rapid increase in roll frequency as fuel is added and thusadequate transverse stability is maintained as fuel is burned withoutthe addition of ballast. In addition, the tumble home configurationreduces the change in roll resistance, roll frequency, and transversestability as fuel is burned and displacement decreases. To ensure goodhead-seas seakeeping, the hull has a large waterplane forward (largerthan present Spruance class destroyers) and a long waterline (Froudenumber at sustained speed <0.38). Moreover, by moving all majormachinery (propulsion and ship-service power generating machinery) andducting out of the midship spaces of the watertight hull, the center ofthe ship is available for personnel working and living areas.

EXAMPLES

The following examples are presented to illustrate the synergisticeffects associated with the various innovative modifications of thepresent invention. Although the present invention is applicable to anylarge, displacement hull design, the following examples are based onhigh speed naval combatant hulls. Each example presents a modificationof the preceding example. All examples incorporate conventional, wellknown machinery and all comparisons are based on conventional, wellknown prediction methods and, thus, details are not provided herein. Ineach case, comparisons are with the preceding example unless otherwisenoted. (Details of weight, fuel consumption, and required powerpredictions are contained in the Appendix B of the aforementioned reportentitled "DD21A--A Capable, Affordable, Modular 21st CenturyDestroyer.")

All examples assume ships having identical military payloads andarmament suites, 30 knot sustained speed at 80% of installed power, and6000 nautical mile (nmi) endurance range (range at 20 knots) except forExamples 9 and 10 having 12,000 nmi endurance ranges. Each ship isdesigned to have the exact power necessary to make the 30 knot sustainedspeed, thus, the engines are rated based on power required. All ships,except for Example 10, are designed for adequate transverse stability atfull-load. Each ship maintains stability equal to the conventional hullof Example 1, thus, each ship has the same ratio of transversemetracentric height to beam (GMT/B=0,075). Example 10 is designed foradequate transverse stability at zero-fuel-load and thus retains someexcess stability at full-load. All ships have a waterline length of 529feet, except for Example 10 whose waterline length is 553 feet.

Examples 1-5 demonstrate the practical limits of beneficial resultsobtainable through introducing modified propulsion and ship-servicemachinery options into standard prior art monohull designs. Themodifications employ existing machinery, arranged in the traditionalmanner in conventional monohulls, i.e., hulls having vertical topsides10, transom sterns 11, conventional powerplants 12 located in the centerof the hulls, and long shafts 14 connecting powerplants 12 andpropellers 30 (see FIGS. 1-4). As shown in FIGS. 3 and 4, all mainpropulsion machinery 22 and ship-service machinery 26, with theexception of a standby ship-service gas turbine driven generator 28located near the stern, are in the machinery box (a series of machineryrooms located near the midships). Main machinery rooms 16 (MMRs) areseparated by three bulkheads. Large vertical trunks , containing intakeducts 18 and exhaust ducts 20, run from the top of the MMRs up throughthe hull and deckhouse. Gears and/or motors are placed low to minimizeshaft angles. Shafts 14 run from the MMRs to strut supported port andstarboard propellers 30.

Example 1

Referring to FIGS. 1-4, Example 1 presents a reference destroyer(hereinafter referred to as REFDD) representing a prior art navalcombatant configuration designed using present Navy design methodology.Lightship displacement (zero-fuel-load, no payload) is 5887 long ton(LT), while full-load displacement is 8174 LT. REFDD carries 1734 LT ofusable fuel. Ship beam at both the design waterline and weather deck is55.5 ft (vertical topsides). Prismatic coefficient (CP) is 0.576 andmaximum section coefficient (CX) is 0.836. REFDD is a conventional,mechanically driven, open-shaft-and-strut destroyer with four GeneralElectric LM2500 simple cycle gas turbine propulsion engines 22 (rated at20,421 horsepower each) driving two controllable-reversible-pitchpropellers 30 (two engines per shaft) through a pair of locked traindouble reduction gears 24 acting as mechanical transmissions. Thereduction gear are located as low as possible in the hull to provide amaximum shaft angle of 3.5°. Separate ship-service power generationmachinery 26 and 28 are provided by three Allison 501K17 gas turbines(rated at 2000 kilowatts each) each geared to a two-pole 60 Hzalternator (i.e., three ship-service turbine-generator sets). All thepropulsion and ship-service engine-generator sets are mounted on steelbedplates having steel pedestals running down to the hull's bottomstructure. Steering is provided by two spade rudders 22 mounted aft ofthe propellers. REFDD is designed, as are all present naval combatants,for stability at full-load. Metracentric height is 4.17 feet.Consequently, REFDD requires seawater ballast to replace fuel in thefuel tanks in order to retain stability and roll frequency throughoutthe mission.

Example 2

Example 2 introduces propulsion derived ship-service power to the shipof Example 1. Two of the ship-service turbine-generator sets arereplaced by 12-pole, variable-speed, constant-frequency (VSCF) liquidcooled alternators connected to the high-speed side of the reductiongear (alternators may alternatively be driven directly by the propulsionturbines). Since engine speed varies, cycloconverters are added toprovide high quality 60 Hz power regardless of alternator speed. Thus,ship-service power is generated by an already operating gas turbine withlower specific fuel consumption than the 501K17 turbines. The overallconsequence is the elimination of two 501K17 engines, a 12 percentreduction in required endurance fuel, and a 4% reduction in bothrequired turbine power and machinery weight. A portion of the fuel muststill be compensated for by addition of seawater into the fuel tanks,however, much of the ballast water can be introduced into clean tanks.

Example 3

The simple-cycle LM2500 gas turbine propulsion engines of Example 2 aredirectly replaced by intercooled, recuperated (ICR) gas turbinespropulsion engines. The propulsion-derived ship-service power systemremains driven by the propulsion engines. Although, due to the heatexchangers, the ICR engines are heavier, they require less airflow and,consequently, reduced ducting. The improved efficiency of the ICRengines results in a 28% reduction in fuel consumption (and, thus, inrequired fuel load) and a 4% reduction in required turbine power. Spaceis freed up to provide sufficient clean water ballast tanks to keep theship at constant stability throughout the mission using clean seawater.ICR gas turbines also have reduced exhaust gas temperatures and, thus,reduced infrared detectability.

Example 4

A direct-drive, solid state-controlled air-cooled AC electric motortransmission replaces each locked-train double reduction gear of Example3. Since the motor can be reversed, fixed-pitch propellers with smallshafting and struts may replace heavier controllable-reversible-pitchpropellers and their larger shafts and struts. Since electricalcross-connection between the two shafts is now possible, three heavilyloaded propulsion engines (each rated at 26,048 hp) diving air-cooledalternators replace the four lighter loaded propulsion engines ofExample 3. The propulsion-derived ship-service power system remainsdriven by the propulsion engines. However, the VSCF system rating isincreased to 4000 kW each so that a single engine may provide allpropulsion and ship-service power during cruise operating conditions (upto 25 knot cruise speed). A 28 ton battery energy storage system permitsoperation on one turbine for cruise, while providing interimship-service power between failure of the operating turbogenerator andstartup of a replacement. This system employs ordinary lead acidbatteries and large inverters that are distributed appropriatelythroughout ship. The result is a 15% reduction in fuel consumption and a2% reduction in required turbine power. However machinery weightincreases because of the large specific weight required by electricmachinery with low rotor tip speeds.

On an electric drive ship, as presented in this and the remainingexamples, a first winding on the armature of the propulsion turbineprovides propulsion power. A second high-voltage winding on the armatureof the existing propulsion turbine may be added to provide high-voltagepower for high energy weapon systems.

Example 5

Example 5 presents the last conventionally configured, open shaft andstrut vessel. The large diameter, low speed direct drive electric motorsand fixed-pitch propellers and shafting of Example 4 are replaced bysmall diameter, high speed electric motors and ring-ring, bicoupled, CRepicyclic reduction gears driving CR propellers, with accompanying CRshafting, seals, and thrust bearings. Increased efficiencies of the CRpropellers and the high-speed motors results in a 15% reduction inrequired power, a 10 percent reduction in fuel consumption, a 9%reduction in machinery weight, and a 6% reduction in both lightship andfull-load displacement.

The overall improvements attributable to the subsystems and componentsof Example 5 over REFDD of Example 1 include 52% reduction in fuelconsumption and 25% reduction in required power at sustained speed.Furthermore, although machinery weight and lightship weight are reducedby 5% and 4%, respectively, due to the reduced fuel load requirements,full-load displacement is reduced by 14%.

Examples 1-5 presented modified machinery options installed inconventionally configured displacement monohulls. While variants on themachinery types involved here could be introduced, the overallimprovement in ship efficiency does not change substantially until a newand innovative approach is taken. Thus, the present invention introducesthe subsystems and components of Example 5 into a ship having radicallydifferent hull and machinery configurations.

Preferred embodiments of the present invention are presented in Examples6-10. The machinery of Example 5 is reconfigured into modular packagesinstalled outside the watertight confines of a new tumble home hull withintegrated superstructure (deckhouse and steeple with identical tumblehome of lower hull). The machinery modules are removable and, thus, donot require drydocking for repair or replacement. In addition, themachinery modules require little shafting (propulsion driveline islocated completely outside the watertight hull) or ducting (verticalintake ducting and side exhaust ducting are located close to enginesthat are mounted outside the watertight hull). Thus, weight required forboth shafting and ducting are drastically reduced, while correspondingsystem efficiency is increased. Moreover, reduced volume requirements ofthe shafting and ducting permit the unconventional tumble home hullconfiguration. Machinery and fuel weight savings and reduced draft allowfurther installed power reduction, uniform lower deck heights, andimproved seakeeping. A further characteristic of the new hull is itsclean, uncluttered configuration having no right-angled intersectionsand few protuberances thus providing minimum radar scattering backtoward either a surface ship, a sea-skimming missile, or a satellite.

EXAMPLE 6

Example 6 presents a modular ship configuration with a tumble homewatertight hull having no major machinery therein. Tumble home angle isconstant at 10°. A composite material steeple 68 of quadrilateralcross-section atop the deckhouse 60 contains the radar and radiocommunication systems in a vertical coaxial configuration. Prismaticcoefficient (CP) is 0.578 and maximum section coefficient (CX) is 0.830.

One ICR gas turbines propulsion engine and its associated propulsionalternator are removed. All other main machinery is retained, i.e., twoICR gas turbines 102 (each rated at 25580 hp) and associated propulsionalternators 106 (AC liquid cooled propulsion generators rated at 28 mWeach), two propulsion derived ship-service power alternators 104 (4000kW each), and one separate ship-service turbine generator set (3000 kW).All are mounted on weather deck 48 in helicopter hanger 62 locatedwithin deckhouse 60. A propulsion alternator 106 and a propulsionderived ship-service power alternator 104, driven by ICR gas turbine102, are mounted on the shaft of each gas turbine 102 to form two powermodules 100. The power modules are fixed to composite material bedplatesmounted directly to the deck. The elimination of steel bedplates andpedestals reduces foundation weight by approximately two-thirds. Eachpower module 100 has short vertical inlet ducting 118, mounted directlyabove the power module air intake, with inlets 116 built into the top ofthe helicopter hanger and having side or aft facing inlet louvers 117.Exhaust ducts 122 may be either through the top of the hangar or,preferably, side mounted to exhaust downward over the side of the tumblehome hull.

Propellers 184, propeller shafts with associated seals and bearings 186,CR gears 192, and geared AC liquid-cooled electric propulsion motors 190(rated at 27.2 mW) are built into capsules 138 that are fitted into twosteerable pods 136, which are part of stern mounted removable propulsormodules 98. Each capsule 138 is inserted into open forward end 180 ofstreamlined cylindrical steerable pod 136, with one acousticallycompliant mounting point forward and one aft. Contrarotating tractorpropellers 184 face directly into the flow stream. The use of electricdrive allows propulsor modules 98 and power modules 100 to beindependently located. Consequently, the pod mounted AC motors areconnected to the AC propulsion generators of the main power modules byelectrical lines only and, thus, the long drive shafts of the previousexamples are eliminated. Synchronous AC electric drive, with identicalhigh-speed, four-pole alternators (located in power modules 100) andmotors (located in propulsor modules 98), provides reasonable efficiencywith great simplicity and low cost. No solid state control is used,thereby minimizing cost, size, weight, acoustic signature, and powerlosses. An increased reduction ratio for low speed operation isavailable by switching the motor windings to provide a large number ofvirtual poles. Pole-switching of the motors provides eight virtual polesfor operation at 6 to 19 knots speed, and damper shields provideinduction-motor torque for startup and low speed reversing. Furthermore,since the steerable pods provide steering control, the two stern mountedspade rudders are eliminated.

All machinery in each power module and propulsor module is pre-alignedand pre-tested prior to installation, thus, reducing expensive and timeconsuming in situ alignment. All modules are installed afterconstruction of the watertight hull has been completed and are piersideinstallable and replaceable.

The reduced resistance of steerable pods compared to open shaft andstrut mounted propellers and stern mounted rudders, and the reduction inweight of the propeller shafting and inlet and exhaust ducts, providesynergistic improvements over conventionally configured hulls. Requiredpower decreases 23%, machinery weight 29%, fuel weight 12%, lightshipdisplacement 19%, full-load displacement 17% and ducting and shaftingweight 81% from the ship of Example 5. Moreover, maneuverability andstealth increase enormously.

Example 7

The separate ship-service turbine generator set of Example 6 provides aredundant ship-service capability and is thus eliminated. Shipdisplacement, fuel load, and required power are reduced accordingly. Theexpanded area of the 17 ft diameter propellers may also be reduced. Byreducing the expanded area ratio from 1.0 to 0.8, incipient cavitationspeed is decreased from 28.6 knots to 25.2 knots (compare this to REFDDwhich cavitates at all speed above endurance speed), however, requiredpower is reduced by 3% and fuel consumption by 2%.

Example 8

As stated earlier, wave resistance increases dramatically withincreasing Froude Number. Furthermore, at low speeds, wave resistancedoes not decrease to zero because the submerged transom produces waves(low speed wave resistance is the price paid by transom stern vesselsfor reducing wavemaking at high speeds). Increasing effective shiplength decreases Froude Number and volumetric coefficient with aresulting decrease in high speed resistance.

A retractable variable angle stern flap 194 is pivotally mounted topropulsor modules 98 of Example 7. The length of the stern flap ispreferably equal to the height of the transom. Thus, ship length can bemaximized when the flap is deployed without increasing air resistancewhen the flap is rotating up against the transom for stowing. In thiscase, the flap is 24 feet in length (equal to the transom height)increasing effective length when deployed to 553 feet. By deploying thestern flap at high speed, effective ship length is increased andresistance decreased. Furthermore, the stern flap offers the opportunityto provide the best effective transom submergence and ship trim at allspeeds.

Example 9

The stern flap equipped ship of Example 8 has a very small fuel loadand, thus, excess fuel capacity. By adding another 787 tons of fuel,ship range can be doubled to 12,000 nmi while maintaining the samehorsepower as the 6000 nmi range no-flap ship. However, with thisconfiguration, there is not enough space for the clean ballast tankagerequired to permit completely clean ballast to compensate for all fuelburned.

Example 10

Example 10 presents an alternative preferred embodiment of the presentinvention. The tumble home hull has a constant tumble home angle of 12°.Prismatic coefficient (CP) is 0.576 and maximum section coefficient (CX)is 0.784. The ship retains the machinery options of Example 9, with thelength increased to 553 feet (length of the previous ship with flapdeployed) and thus has no flap. The ship is designed for adequatetransverse stability with zero-fuel and has a metracentric height of 4.6ft with no fuel aboard. Thus, no seawater ballast is required tomaintain stability throughout the mission. When fuel for 12,000 nmiendurance range is added the metracentric height increases by only 10%to 5.06 ft due to the tumble home hull. Consequently, the roll frequencyincreases by less than 5%, resulting in negligible change in ridecomfort.

Composite material steeple 68 is coupled to deckhouse 60 and supportsvertically coaxial (and, therefore, non-interfering) radar andcommunication antenna 70 in an enclosed environment thereby minimizingmaintenance. Each level of the steeple is selectively shielded withnarrow band-pass aluminized mylar sheets on the inner surface of thesteeple. This material passes specific radar or radio frequencies withlittle attenuation, while reflecting enemy radar. Additionally,individual waveguides and antenna leads in the corners of the steepleclosely couple the antenna to the transmitters powering them, whileminimally affecting the transmission and reception of other coaxiallymounted antenna.

Watertight hull 40, which includes the lower tumble home hull andintegral deckhouse 60, is designed with a continuous steel structure. Asillustrated in FIGS. 11 and 12, main structural members includes twolongitudinally continuous box girders 82 extending upward into thedeckhouse 60 and a longitudinally continuous centerline keel 84.Additional strength members include the outer shell plating 86 (lowerhull and deckhouse) and inner hull sides 88 and bottom 90. Thisstructural configuration provides longitudinal continuity of loadcarrying and is effective in resisting hull bending stresses due towaves of critical length (equal to one ship length) in both hogging(waves high amidships) and sagging (waves high forward and aft)conditions. Furthermore, the continuity of the girders providescontinuous, unobstructed passageways for cables and piping and willsimplify hull assembly and ease the difficulty of identifying andisolating cable and piping faults.

The foregoing series of design innovations results in the presentinvention, a unique ship design where all main machinery is modular andis located outside a watertight tumble home hull. All engines arelocated in the deckhouse, preferably in the helicopter hanger (oralternatively above the aft mounted propulsor modules, or one in thedeckhouse and one above the propulsor module to prevent damage to bothin the event of an explosion). The propulsion driveline is housedoutside the watertight hull in steerable pods.

As compared to the reference destroyer (REFDD), the present invention isslender with a 10% increase in length-to-beam ratio. The ship carriesthe same armament suite but has a lightship displacement of under 4600long tons, a 22% reduction in lightship displacement, with associatedreduction in material costs. Ship volume is decreased by 20%. Therequired power, and thus the required powerplant and fuel expended, arethe major expenses associated with initial and operational costs of theship. The present invention reduces required power at sustained speed by42%, with associated reduction in costs. With intercooled, recuperatedengines it has enough tankage to double the conventional range. Thetumble home hull permits relatively uniform static stability fromfull-load to fuel burn out, thus, no sea water ballast is required. Thesynergistic benefits resulting from the present invention's combinationof a novel machinery configuration with a non-conventional hullconfiguration include reduced power requirements, fuel consumption andcost, increased range, superior stealth, superior seakeeping, reducedenvironmental impact, reduction in the number of gas turbines from sevento two, increased payload capacity per ton of ship displacement, and amore friendly environment for personnel.

The advantages of the present invention are numerous. The presentinvention provides a new ship configuration having simplifiedconstruction, efficient use of midship space for personnel andoperations, easy access to or removal of main machinery allowing majormaintenance without drydocking, and lower initial, operating, andmaintenance costs. Compared to current Naval combatants, the presentinvention provides a ship design of greater simplicity, increased range,greater stealth, increased payload capacity while maintaining reducedlightship displacement, superior seakeeping with no seawater ballast andthus reduced pollution, sharper turns when going either ahead or astern,shorter distance stops, and the same continuous and endurance speedswith reduced installed power and fuel consumption. In the preferredembodiment, two intercooled, recuperated gas turbines replace sevensimple-cycle gas turbines, and deliver the same speed at less than halfthe installed power and fuel consumption, and produce far lesspollution. The ship requires lower manning and fewer auxiliary ships forrefueling. Additionally, preassembled, prealigned and pretestedmachinery saves the enormous cost of aligning machinery in the ship.

These advantages resulted from a synergistic combination of hull,mechanical, and electrical system design modifications thatsimultaneously improved simplicity, efficiency, signatures,maneuverability and seakeeping, weight, and cost. Synergistic designmodifications include adopting a tumble home hull with podded propulsorconfiguration having geared electric drive and CR propellers, removal ofthe major machinery from the hull midships to a point outside thewatertight hull, and making the deckhouse a continuation of the boxgirders. The consequences include simplified propulsion and electricalsystems, short shafting and short ducting that reduce weight andresistance, steerable pods having resistance much lower than openshafting and rudders, and acoustic, radar, and infrared signatures thatalmost automatically improve.

The present invention and many of its attendant advantages will beunderstood from the foregoing description and it will be apparent tothose skilled in the art to which the invention relates that variousmodifications may be made in the form, construction and arrangement ofthe elements of the invention described herein without departing fromthe spirit and scope of the invention or sacrificing all of its materialadvantages. The forms of the present invention herein described are notintended to be limiting but are merely preferred or exemplaryembodiments thereof.

What is claimed is:
 1. A vessel with machinery modules outside awatertight hull, comprising:a watertight hull having a stem bow and atumble home configuration comprising a longitudinally extending hullbottom, port and starboard inward-sloped topsides extending upward fromsaid hull bottom, a longitudinally extending weather deck, and asubstantially vertical aft end; a deckhouse structurally integral withsaid watertight hull, said deckhouse located above said weather deck ata substantially centrally located portion of said vessel; and aplurality of pretested, prealigned propulsion modules mounted outside ofsaid watertight hull, wherein said propulsion modules are installableafter construction of said watertight hull and further wherein saidpropulsion modules are removable and replaceable without drydocking,said propulsion modules comprising: at least one steerable propulsormodule attached to said aft end of said watertight hull, and at leastone power module, each of said power modules in electrical communicationwith one of said propulsor modules, each of said power modules includingtherein power production means for providing ship-service power to saidvessel and propulsion and steering power to said propulsor module.
 2. Avessel as in claim 1 further comprising a composite material steepleattached to said deckhouse, said steeple containing rotating andstationary antennas in coaxial alignment therein and wherein saidinward-sloped topsides have a constant inward-slope angle of betweenabout 10° and about 12° to vertical.
 3. A vessel as in claim 1 whereineach of said at least one steerable propulsor modules comprises:an outerhousing having inward-sloped topsides, said outer housing secured tosaid aft end of said watertight hull and defining a vessel stern; asubstantially vertically aligned rotatable barrel mounted within saidouter housing and containing steering means therein, said steering meansoperative to rotate said rotatable barrel relative to said outerhousing; an axisymmetric pod having an open forward end and a pointedaft end, said pod having mounted therein a prealigned, pretestedintegrated machinery capsule, wherein said integrated machinery capsulecontains at least one rotatably mounted propeller shaft that extendsforward of said pod open forward end, shaft seals, thrust bearings, atleast one propeller mounted to a forward end of said at least onepropeller shaft, and power means functioning to rotate said at least onepropeller; and a streamlined strut rigidly connected at a top end tosaid rotatable barrel and rigidly connected at a bottom end to said pod.4. A vessel as in claim 3 wherein said steering means includes a gearedelectric motor and dynamically balanced, high-reduction-ratio dualorbital gears.
 5. A vessel as in claim 3 wherein said at least onepropeller comprises contrarotating propellers, said at least onepropeller shaft comprises contrarotating propeller shafts, and saidpower means comprise a liquid cooled alternating-current electric motorand a contrarotating reduction gear.
 6. A vessel as in claim 5 whereinsaid contrarotating reduction gear comprises a ring-ring bicoupledcontrarotating epicyclic reduction gear.
 7. A vessel as in claim 3wherein said outer housing defines a transom stern and further wherein aretractable variable angle stern flaps is pivotally mounted to saidouter housing at said transom stern.
 8. A vessel as in claim 1 whereinsaid at least one power module is mounted within said deckhouse andfurther wherein said power production means comprise:a gas turbine; aship-service generator powered by said gas turbine and functioning toprovide ship-service electric power to said vessel; and a propulsiongenerator powered by said gas turbine, said propulsion generatoroperatively connected with said propulsor module to provide electricpower to said propulsor module.
 9. A vessel as in claim 8 wherein saidgas turbine comprises an intercooled, recuperative gas turbine, said gasturbine including an intercooler integral with said gas turbine, and arecuperator integral with said gas turbine.
 10. A vessel as in claim 1wherein said at least one power module is mounted atop said at least onepropulsor modules and further wherein said power production meanscomprise:a gas turbine; a ship-service generator powered by said gasturbine and functioning to provide ship-service power to said vessel;and a propulsion generator powered by said gas turbine, said propulsiongenerator operatively connected with said propulsor module to provideelectric power to said propulsor module.
 11. A vessel as in claim 10wherein said gas turbine comprises an intercooled, recuperative gasturbine, said gas turbine including an intercooler integral with saidgas turbine, and a recuperator integral with said gas turbine.
 12. Avessel as in claim 1 wherein said at least one power module includesfirst and second power modules, wherein said first power module ismounted within said deckhouse and said second power module is mountedatop one of said at least one propulsor modules, and further whereinsaid power production means comprise:a gas turbine; a ship-servicegenerator powered by said gas turbine and functioning to provideship-service power to said vessel; and a propulsion generator powered bysaid gas turbine, said propulsion generator operatively connected withsaid propulsor module to provide electric power to said propulsormodule.
 13. A vessel as in claim 12 wherein said gas turbine comprisesan intercooled, recuperative gas turbine, said gas turbine including anintercooler integral with said gas turbine, and a recuperator integralwith said gas turbine.
 14. A vessel as in claim 1 further comprising abattery energy storage system for providing ship-service power in theevent said ship-service generator fails or is taken off line.
 15. Avessel as in claim 1 further comprising at least one short over-the-sideexhaust duct, each of said at least one short over-the-side exhaust ductlocated adjacent to one of said at least one power module and in flowcommunication with an exhaust of one of said at least one power module,and each of said at least one short over-the-side exhaust duct includinga boundary-layer induction signature suppressor and a radar reflectingexhaust cap.
 16. A vessel as in claim 1 further comprising:primarystructural members including two longitudinally continuous box girdersand a longitudinally continuous keel, said box girders and keelextending substantially from said bow to said aft end of said watertighthull, said box girders defining an intersection of said inward-slopedtopsides and said weather deck, a portion of said box girder adjacentsaid deckhouse extending upward from said weather deck substantially toa top of said deckhouse and defining longitudinally extendinginward-sloped sides of said deckhouse.
 17. A vessel as in claim 1wherein said watertight hull is separated longitudinally into aplurality of survivable watertight compartments, each of saidcompartments having at least one auxiliary machinery module mountedtherein, said at least one auxiliary machinery module including heatingmeans, air conditioning means, ventilation means, fire suppressionmeans, and backup electric power means.
 18. A vessel as in claim 17further comprising:primary structural members comprising twolongitudinally continuous box girders and a longitudinally continuouskeel, said box girders and keel extending substantially from said bow tosaid aft end of said watertight hull, said box girders defining anintersection of said inward-sloped topsides and said weather deck andextending from said weather deck downward one deck, a portion of saidbox girder adjacent said deckhouse extending upward from said weatherdeck substantially to a top of said deckhouse and defininglongitudinally extending inward-sloped sides of said deckhouse, said boxgirders contain a plurality of longitudinally extending cables and pipestherein; a plurality of watertight insulated electrical connector plugspenetrating a wall of at least one of said box girders, at least one ofsaid plugs located adjacent each of said compartments, each of saidplugs being in electrical communication with at least one of saidlongitudinally extending cables and further being in electricalcommunication with at least one cable in one of said compartments; and aplurality of transverse pipes penetrating a wall of at least one of saidbox girders, at least one of said pipes located adjacent each of saidcompartments, each of said transverse pipes including a sealing meansthereon operative to create a watertight seal between said transversepipe and said box girder, each of said transverse pipes being in flowcommunication with at least one of said longitudinal pipes and furtherbeing in flow communication with at least one pipe in one of saidcompartments, each of said transverse pipes including a shut-off valveon each side of said wall of said box girder.
 19. A vessel as in claim 1further comprising flared topsides below said weather deck and flaredbulwarks above said weather deck, said flared topsides and bulwarksextending aft from said stem bow.
 20. A vessel as in claim 3 whereinsaid streamlined strut includes port and starboard ejection ports and acirculation control valve for preferentially ejecting water through saidejection ports to provide steering control by way of circulation controlthrough the Coanda effect.
 21. A high speed naval combatant,comprising:a watertight hull having a stem bow and a tumble homeconfiguration comprising a longitudinally extending hull bottom, portand starboard inward-sloped topsides, a longitudinally extending weatherdeck, and a substantially vertical aft end, said watertight hullseparated longitudinally into a plurality of survivable watertightcompartments, each of said compartments having at least one auxiliarymachinery module mounted therein, said at least one auxiliary machinerymodule including heating means, air conditioning means, ventilationmeans, fire suppression means, and backup electric power means; adeckhouse structurally integral with said watertight hull, saiddeckhouse located above said weather deck at a substantially centrallylocated portion of said vessel, said deckhouse including a helicopterhanger; a composite material steeple attached to said deckhouse, saidsteeple containing rotating and stationary antennas in coaxial alignmenttherein, each of said antenna transmitting within a narrow frequencyrange, inside walls of said composite material steeple havingradar-reflective materials thereon, said materials operative to reflectradar originating from without said vessel but allowing a narrow-bandtransmission from said antennas; and a plurality of pretested,prealigned propulsion modules mounted to an outer surface of saidwatertight hull, wherein said propulsion modules are installable afterconstruction of said watertight hull and further wherein said propulsionmodules are removable and replaceable without drydocking, saidpropulsion modules comprising: at least one steerable propulsor moduleattached to said aft end of said watertight hull, said at least onesteerable propulsor module including:an outer housing secured to saidaft end of said watertight hull and defining a vessel stern, asubstantially vertical rotatable barrel mounted within said outerhousing and containing steering means therein, said steering meansincluding a geared electric motor and dynamically balanced,high-reduction-ratio dual orbital gears functioning to rotate saidrotatable barrel relative to said outer housing, an axisymmetric podhaving an open forward end and a pointed aft end, said pod havingmounted therein a prealigned, pretested integrated machinery capsule,said integrated machinery capsule containing contrarotating propellershafts that extend forward of said pod open forward end, shaft seals,thrust bearings, contrarotating propellers mounted on a forward end ofsaid contrarotating propeller shafts, a liquid cooledalternating-current electric motor and a contrarotating reduction gearfunctioning to rotate said contrarotating propellers, and a streamlinedstrut rigidly connected at a top end to said rotatable barrel andrigidly connected at a bottom end to said pod, wherein said streamlinedstrut includes port and starboard ejection ports and a circulationcontrol valve for preferentially ejecting water through said ejectionports to provide steering control by way of circulation control throughthe Coanda effect; and at least one power module mounted within saidhelicopter hanger, each power module including:an intercooled,recuperative engine including a gas turbine, an intercooler integralwith said gas turbine, and a recuperator integral with said gas turbine,a ship-service generator powered by said engine and functioning toprovide ship-service electric power to said naval combatant, and apropulsion generator having a first winding powered by said engine andoperatively connected with said propulsor module to provide electricpower to said propulsor module, and a second, coaxial high voltagewinding capable of powering high energy weapon systems.
 22. A navalcombatant as in claim 21 wherein said inward-sloped topsides have aconstant inward-slope angle of between about 10° and about 12°, andwherein said naval combatant further includes flared topsides below saidweather deck and flared bulwarks above said weather deck, said flaredtopsides and bulwarks extending aft from said stem bow.
 23. A high speednaval combatant as in claim 22 further comprising:primary structuralmembers comprising two longitudinally continuous box girders and alongitudinally continuous keel, and strength members comprising outershell plating, and inner hull sides and bottom, said box girders andkeel extending substantially from said bow to said aft end of saidwatertight hull, said box girders define an intersection of saidinward-sloped topsides and said weather deck and extending from saidweather deck downward one deck, a portion of said box girder adjacentsaid deckhouse extending upward from said weather deck substantially toa top of said deckhouse and defining longitudinally extendinginward-sloped sides of said deckhouse, said box girders contain aplurality of longitudinally extending cables and pipes therein, at leastone of said box girders contains longitudinal walkways functioning toprovide personnel access among said plurality of survivablecompartments; a plurality of watertight insulated electrical plugconnectors penetrating a wall of each box girder, at least one of saidplugs located adjacent each of said compartments, each of said plugsbeing in electrical communication with at least one of saidlongitudinally extending cables and further being in electricalcommunication with at least one cable in one of said compartments; and aplurality of transverse pipes penetrating a wall of each box girder, atleast one of said transverse pipes located adjacent each of saidcompartments, each of said transverse pipes including a sealing meansthereon operative to create a watertight seal between said transversepipe and said box girder, each of said transverse pipe being in flowcommunication with at least one longitudinal pipe and further being inflow communication with at least one pipe in one of said compartments,each of said transverse pipe including a shut-off valve on each side ofsaid wall of said box girder.